"About a week ago... we were overrun by local criminal militia. They were coming on site with guns and knives, and intimidating and threatening - loosening off rounds."

The Foreign Office made arrangements to evacuate people from that region, he said, adding that their rescuers were "magic people".

"They're the best in the world. You know we owe them perhaps our lives. We don't know. But they were certainly risking theirs."

Embassy closed

Those on board HMS Cumberland will be met in Malta, after a 12-hour sea journey - and flown to the UK on Monday or Tuesday.

The government said HMS York remained in the region and was "ready to assist as required".

Analysis

By Joe LynamBBC News

It is not unprecedented for the assets of a ruling family to be frozen by UK authorities while they are still in power. The ruling junta in Burma, Saddam Hussein and President Milosevic of Serbia have all endured (or continue to endure) that in the past.

What is interesting is the co-ordinated way in which the Treasury, BIS and FCO have been working on this order behind the scenes for a few days - directly liaising with Britain's largest banks as well as the FSA, BBA and Bank of England.

As soon as all Britons had been extracted out of Libya and the legal permission had been given by the UN, the asset freezing order took effect tonight.

While is it unclear exactly how much Libyan assets in the UK are worth, we can safely say it's in the "hundreds of millions".

Some reports have said that Col Gaddafi's son Saif owns a plush house in Hampstead, north London, but most of the assets are probably of the paper variety.

The FCO is also urging those who have already left Libya to contact them on 0207 008 0000 to ensure they have been accounted for.

About 100,000 people have fled anti-government unrest in Libya over the past week, the UN estimates.

As the Libyan leader, Col Muammar Gaddafi, battles for political survival amid an uprising that began in the east of the country, the UK's foreign secretary said it was time for him to step down.

William Hague told the BBC: "Of course, it is time for Col Gaddafi to go, that is the best hope for Libya."

The UK has frozen his British-held assets and those of his family, and withdrawn their diplomatic immunity on British soil.

It followed UN Security Council sanctions agreed on Saturday backing an arms embargo and asset freeze, and referring Col Gaddafi to the International Criminal Court for alleged crimes against humanity.

Business Secretary Vince Cable has also banned the unlicensed export of any uncirculated Libyan banknotes.

It came after the Libyan regime had asked to ship an estimated £900m worth of British-printed banknotes to Tripoli.

The Foreign Office has closed the British embassy in Tripoli, leaving a skeleton staff working in a different building.